The present application relates generally to the operation of flash memory, and more specifically to coordinating internal operations with commands received by a host.
A non-volatile memory system such as a flash memory card or drive is used by a host to store information. Therefore, a command received by the host should be serviced quickly and typically will have priority over whatever other operations may be taking place within the system.
Non-volatile memory storage systems may receive, transmit, or issue operations or instructions required to manage data in the memory. Most memory operations received or issued by the non-volatile memory storage system are executed immediately. However, due to different timing limitations (e.g., initialization timeout, write command timeout limitations, and other timing limitations), there might not be enough time allocated to completely execute a memory operation. As a result, the execution of the memory operation may be deferred until the next available timeslot or ignored until the next time the memory operation is triggered. A garbage collection operation is an operation initiated internally (not by a host) to manage the data of the memory system and ensure its reliability. Such operations are initiated by the controller and/or system firmware.
Currently, the memory operations are temporarily stored in the random access memory (RAM) of the non-volatile memory storage system. However, the RAM is configured to store only one of each type of deferred memory operation. For example, if the non-volatile memory storage system needs to refresh a block and, as a result, triggers a garbage collection operation, the garbage collection operation can be stored in the RAM and deferred for execution at a later time. On the other hand, if the non-volatile memory storage system needs to refresh two blocks, both garbage collection operations associated with the refreshes are not stored in the RAM. Furthermore, once a power loss occurs, the information stored in the RAM is lost and the memory operation will not be executed until the next time such memory operation is triggered. Such loss of information can lead to access errors and reduce the reliability of the non-volatile memory storage system. As a result, continuing efforts are being made to improve the storage and processing of memory operations in the non-volatile memory storage system.